Electronic device with isolated cavity antennas

ABSTRACT

An electronic device may have a metal housing. The metal housing may have an upper housing in which a component such as a display is mounted and a lower housing in which a component such as a keyboard is mounted. Hinges may be used to mount the upper housing to the lower housing for rotation about a rotational axis. A slot-shaped opening may separate the upper and lower housing. A flexible printed circuit with ground traces may bisect the slot-shaped opening to form first and second slots. Cavity antennas may be aligned with the slots. Each cavity antenna may include a hollow carrier with a pair of speakers. The speakers may have ports that emit sound through aligned openings in the lower housing. Conductive gaskets surrounding the ports may acoustically seal the speaker ports while shorting the cavity antenna to the lower housing.

BACKGROUND

This relates generally to electronic devices and, more particularly, towireless electronic devices with antennas.

Electronic devices often include antennas. For example, cellulartelephones, computers, and other devices often contain antennas forsupporting wireless communications.

It can be challenging to form electronic device antenna structures withdesired attributes. In some wireless devices, the presence of conductivehousing structures can influence antenna performance. Antennaperformance may not be satisfactory if the housing structures are notconfigured properly and interfere with antenna operation. Device sizecan also affect performance. It can be difficult to achieve desiredperformance levels in a compact device, particularly when the compactdevice has conductive housing structures.

It would therefore be desirable to be able to provide improved wirelesscircuitry for electronic devices.

SUMMARY

An electronic device may have a metal housing. The metal housing mayhave an upper housing portion such as a lid in which a component such asa display is mounted. The metal housing may have a lower housing portionsuch as a base housing containing a component such as a keyboard. Hingesmay be used to mount the upper housing portion to the lower housingportion. The upper housing portion may be rotated relative to the lowerhousing portion using the hinges.

A slot-shaped opening may separate the upper and lower housing portions.The slot-shaped opening may be present both when the lid is open andwhen the lid is closed. A flexible printed circuit with ground tracesmay bisect the slot-shaped opening to form first and second slots. Afirst of the hinges and a first ground trace on the flexible printedcircuit may form opposing ends of the first slot. A second of the hingesand a second ground trace on the flexible printed circuit may formopposing ends of the second slot. Signal traces on the flexible printedcircuit may be interposed between the first and second ground traces.

Cavity antennas may be aligned with the slots, which serve as aperturesfor the antennas. Each cavity antenna may include a hollow carrier witha pair of speakers. The speakers may have ports that emit sound throughaligned openings in the lower housing. Conductive gaskets surroundingthe ports may acoustically seal the speaker ports while shorting thecavity antennas to the lower housing.

An angle sensor may be used to measure the angle between the upperhousing portion and the lower housing portion. Control circuitry maytune the antennas using tunable circuitry. The control circuitry maytune the antennas based on measurements made using a lid angle sensor orother circuitry.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative electronic device suchas a laptop computer in accordance with an embodiment.

FIG. 2 is a schematic diagram of an illustrative electronic device withwireless circuitry in accordance with an embodiment.

FIG. 3 is a perspective view of an illustrative antenna and associatedtransceiver circuitry that may be used in an electronic device of thetype shown in FIG. 1 in accordance with an embodiment.

FIG. 4 is a graph in which antenna performance (standing wave ratio SWR)has been plotted as a function of operating frequency for anillustrative antenna of the type shown in FIG. 3 in accordance with anembodiment.

FIG. 5 is a perspective view of an illustrative antenna with a cavitythat has been formed from metal traces on a dielectric carrier that alsoserves as a speaker box in accordance with an embodiment.

FIG. 6 is a cross-sectional side view of an illustrative cavity antennasuch as the cavity antenna of FIG. 5 showing how the interior of thedielectric carrier may serve as speaker volumes for a pair of speakersin accordance with an embodiment.

FIG. 7 is a perspective view of a rear edge portion of an illustrativelaptop computer showing how a slot-shaped opening may be present throughwhich antenna signals may pass when the lid of the laptop computer isclosed in accordance with an embodiment.

FIG. 8 is a top view of an illustrative interior portion of a laptopcomputer showing how antennas may be located on either side of thecomputer housing and may operate through slot apertures that areisolated from each other by ground traces on the edges of flexibleprinted circuit structures in accordance with an embodiment.

FIG. 9 is a side view of an illustrative stack of conductive gasketmaterials that may be used in forming a conductive gasket in accordancewith an embodiment.

FIG. 10 is a cross-sectional side view of an illustrative laptopcomputer showing how an antenna may be grounded using a conductivespeaker gasket and may operate through a slot aperture between a lid andbase housing for the laptop computer when the lid is in a closedposition in accordance with an embodiment.

FIG. 11 is a cross-sectional side view of an illustrative laptopcomputer showing how an antenna may be grounded using a conductivespeaker gasket and may operate through a pair of slot apertures betweena lid and base housing for the laptop computer when the lid is in anopen position in accordance with an embodiment.

FIG. 12 is a graph in which antenna performance (standing-wave ratioSWR) has been plotted as a function of frequency to show how antennabandwidth may be enlarged to accommodate potential detuning duringoperation in accordance with an embodiment.

FIG. 13 is a graph in which antenna efficiency has been plotted as afunction of lid angle for different antenna configurations in accordancewith an embodiment.

FIG. 14 is a schematic diagram showing how an antenna may have a tuningcircuit that is adjusted based on lid angle in accordance with anembodiment.

FIG. 15 is a diagram of an illustrative tunable cavity antenna that maybe tuned based on sensed lid angle in accordance with an embodiment.

FIG. 16 is a graph in which antenna performance (standing-wave ratioSWR) has been plotted as a function of frequency under differentoperating conditions and tuning settings in accordance with anembodiment.

DETAILED DESCRIPTION

An electronic device such as electronic device 10 of FIG. 1 may containwireless circuitry. For example, electronic device 10 may containwireless communications circuitry that operates in long-rangecommunications bands such as cellular telephone bands and wirelesscircuitry that operates in short-range communications bands such as the2.4 GHz Bluetooth® band and the 2.4 GHz and 5 GHz WiFi® wireless localarea network bands (sometimes referred to as IEEE 802.11 bands orwireless local area network communications bands). Device 10 may alsocontain wireless communications circuitry for implementing near-fieldcommunications, communications at 60 GHz, light-based wirelesscommunications, satellite navigation system communications, or otherwireless communications.

Device 10 may be a handheld electronic device such as a cellulartelephone, media player, gaming device, or other device, may be a laptopcomputer, tablet computer, or other portable computer, may be a desktopcomputer, may be a computer display, may be a display containing anembedded computer, may be a television or set top box, or may be otherelectronic equipment. Configurations in which device 10 has a rotatablelid as in a portable computer are sometimes described herein as anexample. This is, however, merely illustrative. Device 10 may be anysuitable electronic equipment.

As shown in the example of FIG. 1, device 10 may have a housing such ashousing 12. Housing 12 may be formed from plastic, metal (e.g.,aluminum), fiber composites such as carbon fiber, glass, ceramic, othermaterials, and combinations of these materials. Housing 12 or parts ofhousing 12 may be formed using a unibody construction in which housingstructures are formed from an integrated piece of material. Multiparthousing constructions may also be used in which housing 12 or parts ofhousing 12 are formed from frame structures, housing walls, and othercomponents that are attached to each other using fasteners, adhesive,and other attachment mechanisms.

Some of the structures in housing 12 may be conductive. For example,metal parts of housing 12 such as metal housing walls may be conductive.Other parts of housing 12 may be formed from dielectric material such asplastic, glass, ceramic, non-conducting composites, etc. To ensure thatantenna structures in device 10 function properly, care should be takenwhen placing the antenna structures relative to the conductive portionsof housing 12. If desired, portions of housing 12 may form part of theantenna structures for device 10. For example, conductive housingsidewalls may form all or part of an antenna ground. The antenna groundinclude one or more cavities for cavity-backed antennas. The cavities inthe cavity-backed antennas may be formed from metal traces on dielectriccarriers and may be electrically shorted to portions of housing 12 neara slot-shaped opening between the upper and lower portions of thehousing.

As shown in FIG. 1, device 10 may have input-output devices such astrack pad 18 and keyboard 16. Device 10 may also have components such asa camera, microphones, speakers, buttons, removable storage drives,status indicator lights, buzzers, sensors, and other input-outputdevices. These devices may be used to gather input for device 10 and maybe used to supply a user of device 10 with output. Ports in device 10may receive mating connectors (e.g., an audio plug, a connectorassociated with a data cable such as a Universal Serial Bus cable, adata cable that handles video and audio data such as a cable thatconnects device 10 to a computer display, television, or other monitor,etc.).

Device 10 may include a display such a display 14. Display 14 may be aliquid crystal display (LCD), a plasma display, an organiclight-emitting diode (OLED) display, an electrophoretic display, or adisplay implemented using other display technologies. A touch sensor maybe incorporated into display 14 (i.e., display 14 may be a touch screendisplay) or display 14 may be insensitive to touch. Touch sensors fordisplay 14 may be resistive touch sensors, capacitive touch sensors,acoustic touch sensors, light-based touch sensors, force sensors, ortouch sensors implemented using other touch technologies.

Device 10 may have a one-piece housing or a multi-piece housing. Asshown in FIG. 1, for example, electronic device 10 may be a device suchas a portable computer or other device that has a two-part housingformed from an upper housing portion such as upper housing 12A and lowerhousing portion such as lower housing 12B. Upper housing 12A may includedisplay 14 and may sometimes be referred to as a display housing or lid.Lower housing 12B may sometimes be referred to as a base housing or mainhousing.

Housings 12A and 12B may be connected to each other using hingestructures located in region 20 along the upper edge of lower housing12B and the lower edge of upper housing 12A). For example, housings 12Aand 12B may be coupled by hinges 26. Hinges 26 may be located atopposing left and right edges of housing 12 along hinge axis 22. Aslot-shaped opening such as opening (slot) 30 may be formed betweenupper housing 12A and lower housing 12B and may be bordered on eitherend by hinges 26. Hinges 26, which may be formed from conductivestructures such as metal structures, may allow upper housing 12A torotate about axis 22 in directions 24 relative to lower housing 12B. Theplane of lid (upper housing) 12A and the plane of lower housing 12B maybe separated by an angle that varies between 0° when the lid is closedto 90°, 140°, or more when the lid is fully opened.

Metal traces on one or more flexible printed circuits 31 may bisect slot30 and thereby create two slots 30-1 and 30-2. Slots 30-1 and 30-2 maybe surrounded by metal. For example, slots 30-1 and 30-2 may besurrounded by metal portions of housing 12A and 12B on their top andbottom edges and hinges 26 and flexible printed circuit traces onflexible printed circuit(s) 31 on their opposing ends). Slots 30-1 and30-2 may serve as antenna apertures for respective antennas 40 in device10. These antennas may be used to form a multiple-input-multiple-output(MIMO) antenna array.

Speakers in device 10 may be located within housing 12. Housing 12 mayhave perforations such as circular holes or may have other speakeropenings to allow sound to exit the interior of device 10. Arrays ofspeaker openings (e.g., circular holes or other housing openings) may beformed on the left and right edges of housing 12B (e.g., in positionsflanking the right and left sides of keyboard 16), may be formed alongthe upper edge of housing 12B adjacent to hinge region 20, or may beformed in other suitable locations. Device 10 may have one or morespeakers, two or more speakers, three or more speakers, four or morespeakers, or other suitable numbers of speakers. In the example of FIG.1, speaker openings 28 have been formed in four groups (clusters) eachof which overlaps a respective speaker in a group of four speakers thathave been mounted within the interior of device 10. If desired, dummyopenings (i.e., housing openings that do not overlap any speakers) maybe formed within housing 12 between respective groups of speaker holes28, so that housing 12B appears to have a single uninterrupted band ofspeaker perforations running along the upper edge of housing 12B nearhinge axis 22. The configuration of FIG. 1 in which speaker openings 28are formed in four different speaker locations is merely illustrative.

A schematic diagram showing illustrative components that may be used indevice 10 is shown in FIG. 2. As shown in FIG. 2, device 10 may includecontrol circuitry such as storage and processing circuitry 30. Storageand processing circuitry 30 may include storage such as hard disk drivestorage, nonvolatile memory (e.g., flash memory or otherelectrically-programmable-read-only memory configured to form a solidstate drive), volatile memory (e.g., static or dynamicrandom-access-memory), etc. Processing circuitry in storage andprocessing circuitry 30 may be used to control the operation of device10. This processing circuitry may be based on one or moremicroprocessors, microcontrollers, digital signal processors,application specific integrated circuits, etc.

Storage and processing circuitry 30 may be used to run software ondevice 10, such as internet browsing applications,voice-over-internet-protocol (VOIP) telephone call applications, emailapplications, media playback applications, operating system functions,etc. To support interactions with external equipment, storage andprocessing circuitry 30 may be used in implementing communicationsprotocols. Communications protocols that may be implemented usingstorage and processing circuitry 30 include internet protocols, wirelesslocal area network protocols (e.g., IEEE 802.11 protocols—sometimesreferred to as WiFi®), protocols for other short-range wirelesscommunications links such as the Bluetooth® protocol, cellular telephoneprotocols, MIMO protocols, antenna diversity protocols, etc.

Input-output circuitry 44 may include input-output devices to allow datato be supplied to device 10 and to allow data to be provided from device10 to external devices. Input-output devices in circuitry 44 may includeuser interface devices, data port devices, and other input-outputcomponents. For example, input-output devices in circuitry 44 mayinclude touch screens, displays without touch sensor capabilities,buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards,cameras, buttons, status indicators, light sources, audio jacks andother audio port components, digital data port devices, light sensors,motion sensors (accelerometers), capacitance sensors, proximity sensors,audio circuitry 32 such as microphones and speakers, and othercomponents.

Input-output circuitry 44 may include wireless communications circuitry34 for communicating wirelessly with external equipment. Wirelesscommunications circuitry 34 may include radio-frequency (RF) transceivercircuitry formed from one or more integrated circuits, power amplifiercircuitry, low-noise input amplifiers, passive RF components, one ormore antennas, transmission lines, and other circuitry for handling RFwireless signals. Wireless signals can also be sent using light (e.g.,using infrared communications).

Wireless communications circuitry 34 may include radio-frequencytransceiver circuitry for handling voice data and non-voice data invarious radio-frequency communications bands. For example, circuitry 34may include wireless local area network transceiver circuitry to handle2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and tohandle the 2.4 GHz Bluetooth® communications band. Circuitry 34 mayinclude cellular telephone transceiver circuitry for handling wirelesscommunications in frequency ranges such as a low communications bandfrom 700 to 960 MHz, a midband from 1710 to 2170 MHz, and a high bandfrom 2300 to 2700 MHz or other communications bands between 700 MHz and2700 MHz or other suitable frequencies (as examples).

Wireless communications circuitry 34 may include circuitry for othershort-range and long-range wireless links if desired. For example,wireless communications circuitry 34 may include 60 GHz transceivercircuitry, circuitry for receiving television and radio signals, pagingsystem transceivers, near field communications (NFC) circuitry, etc.Wireless communications circuitry 34 may include satellite navigationsystem circuitry such as global positioning system (GPS) receivercircuitry for receiving GPS signals at 1575 MHz or for handling othersatellite positioning data. In WiFi® and Bluetooth® links and othershort-range wireless links, wireless signals are typically used toconvey data over tens or hundreds of feet. In cellular telephone linksand other long-range links, wireless signals are typically used toconvey data over thousands of feet or miles.

Wireless communications circuitry 34 may include antennas 40. Antennas40 may be formed using any suitable antenna types. For example, antennas40 may include antennas with resonating elements that are formed fromloop antenna structures, patch antenna structures, inverted-F antennastructures, slot antenna structures, planar inverted-F antennastructures, helical antenna structures, hybrids of these designs, etc.If desired, one or more of antennas 40 may be cavity-backed antennas.Different types of antennas may be used for different bands andcombinations of bands. For example, one type of antenna may be used informing a local wireless link antenna and another type of antenna may beused in forming a remote wireless link antenna.

If desired, antennas 40 may include one or more inverted-F antennas withparasitic resonating elements. This type of illustrative antennaconfiguration is shown in FIG. 3. As shown in FIG. 3, antenna 40 mayinclude antenna resonating element 50 and antenna ground 52. Antennaresonating element 50 may have one or more branches such as branches50-1 and 50-2. Branch 50-1 may handle lower frequencies (e.g., 2.4 GHz)and branch 50-2 may handle higher frequencies (e.g., 5 GHz) or branches50-1 and 50-2 may resonate in other suitable communications bands.Parasitic antenna resonating element 58 may be an L-shaped metal elementthat is terminated at ground 52. The presence of element 58 may helpbroaden the bandwidth of antenna 40 (e.g., in high frequency band suchas a 5 GHz band).

Antenna 40 may have a return path such as short circuit path 54 that iscoupled between antenna resonating element 50 and ground 52. Antennafeed 56 may have positive antenna feed terminal 98 and ground antennafeed terminal 100 and may be coupled between resonating element 50 andground 52 in parallel with return path 54.

Transmission line paths such as transmission line 92 may be used tocouple antenna structures 40 to transceiver circuitry such astransceiver circuitry 90. Transmission line 92 may have a positivetransmission line path such as path 94 that is coupled to positiveantenna feed terminal 98 and a ground transmission line path such aspath 96 that is coupled to ground antenna feed terminal 100. Transceivercircuitry 90 may operate at wireless local area network bands such asthe 2.4 GHz and 5 GHz bands or other suitable short-range or long-rangecommunications bands. Transmission lines in device 10 such astransmission line 92 may include coaxial cable paths, microstriptransmission lines, stripline transmission lines, edge-coupledmicrostrip transmission lines, edge-coupled stripline transmissionlines, transmission lines formed from combinations of transmission linesof these types, etc. Filter circuitry, switching circuitry, impedancematching circuitry, and other circuitry may be interposed within thetransmission lines, if desired. As an example, a circuit component suchas capacitor 102 or other circuitry may be interposed in positivetransmission line path 94 or elsewhere within transmission line 92between transceiver circuitry 90 and antenna 40. Capacitor 102 may helpbroaden the bandwidth of antenna 40 so that antenna performance issatisfactory over a range of operating conditions for device 10 (e.g.,operations at various lid angles for lid 12A relative to base 12B).

FIG. 4 is a graph in which antenna performance (i.e., standing waveratio SWR) has been plotted as a function of operating frequency f forantenna 40 of FIG. 3. Curve 60 shows how antenna 40 may operate in a lowfrequency band such as a 2.4 GHz band (e.g., to support WiFi® orBluetooth® signals). Low band performance (curve 60) may be supportedusing low band arm 50-1 of antenna resonating element 50. Curve 62 maycorrespond to the coverage of antenna 40 that is supported by high bandarm 50-2 of antenna 40 (e.g., the response of antenna resonating element50 at 5 GHz). Curve 64 shows how a slightly shifted high band resonancemay be supported using parasitic antenna resonating element 58. Element50 may be directly feed at antenna feed 56 using transmission line 92.Parasitic element 58 is not directly fed, but rather is coupled toantenna resonating element 50 through electromagnetic near-fieldcoupling. The overall response of antenna 40 in its high band at 5 GHz,which is represented by curve 66, is characterized by both acontribution from antenna resonating element 50 (curve 62) and acontribution from parasitic antenna resonating element 58 (curve 64).The presence of element 58 helps broaden the high band response ofantenna 40 to ensure that the high band is covered satisfactorily.

Antenna 40 may be formed from metal traces on a dielectric supportstructure. The dielectric support structure may be formed from ceramic,plastic, foam, glass, other dielectric materials, or combinations ofthese materials. Illustrative configurations in which the dielectricsupport structure is plastic support structure may sometimes bedescribed herein as an example. FIG. 5 is a perspective view of anillustrative antenna formed from patterned metal traces on a plasticsupport (sometimes referred to as an antenna carrier). In the example ofFIG. 5, support structure 76 forms an antenna carrier for metal antennatraces. The metal traces may be patterned using laser patterningtechniques such as techniques in which selected portions of a plasticsurface are activated and become coated with metal during subsequentelectroplating operations. If desired, other techniques for formingantenna 40 may be used (e.g., techniques such as machining, attachmentof patterned metal foil, mounting of patterned flexible printedcircuits, etc.).

In the example of FIG. 5, the metal antenna traces on plastic supportstructure 76 include traces that form antenna ground 52, antennaresonating element 50, and parasitic antenna resonating element 58.Support structure 76 may be a hollow box-shaped structure or otherstructure having exterior surfaces surrounding a hollow interior.Structure 76 may be, for example, a six sided box. Metal traces may bepatterned on structure 76 so that ground 52 forms a grounded antennacavity. For example, ground traces 52 may be formed on five of the sixsides of the box. The front face of support 76 (in the orientation ofFIG. 5) may be free of ground traces and may be used to support metaltraces that form antenna resonating element 50 and parasitic element 58,as shown in FIG. 5. In this type of configuration, metal traces 52 forman antenna cavity and antenna 40 is a cavity-backed antenna (i.e.,antenna 40 is a cavity antenna). Transmission line 92 may be formed froma coaxial cable that is coupled to antenna 40 at feed 56 (terminals 98and 100).

In addition to serving as an antenna carrier for antenna 40, supportstructure 76 may serve as a speaker enclosure (sometimes referred to asa speaker box). As shown in FIG. 5, support structure 76 may serve as aspeaker enclosure for a pair of speakers 70. Speakers 70 may be formedfrom speaker drivers located at opposing ends of structure 76. Theinterior of structure 76 may be divided into separate volumes for thespeakers. Each of speakers 70 may emit sound through a respective one ofports 72. Ports 72 may be covered with a layer of open cell foam, ametal or plastic mesh, or other structures for preventing dust intrusioninto the interior of structure 76 or, if desired, ports 72 may have oneor more open areas (i.e., areas not covered with mesh) that allow soundto exit speakers 70.

To create a satisfactory acoustic and electrical seal with housing 12,each speaker port 72 may be surrounded by a gasket such as gasket 74.Gaskets 74 may be ring shaped conductive compressible structures. If,for example, speaker ports 72 have rectangular shapes, gaskets 74 mayhave the shapes of rectangular rings. Gaskets 74 may be formed from oneor more layers of conductive foam, conductive fabric, layers thatinclude conductive vias and other conductive structures, conductiveadhesive, and other conductive structures that allow gaskets 74 to formacoustic seals around speaker ports 72 while electrically shortingantenna traces such as ground trace 52 to housing 12. The seal formedaround speaker ports 72 by gaskets 74 helps prevent dust and sound fromentering into the interior of housing 12. Gaskets 74 also help groundantenna ground traces 52 on support structure 76 to metal housing 12,which may serve as a portion of the ground for antenna 40. The presenceof conductive gaskets 74 may also help prevent radio-frequency antennasignals that are emitted by antenna 40 from being coupled into theinterior of housing 12 as signal noise.

FIG. 6 is a cross-sectional side view of antenna 40 of FIG. 5 takenalong line 80 and viewed in direction 82. As shown in FIG. 6, theinterior of hollow support structure 76 may be separated into individualcavities 130-1 and 130-2 by a divider structure such as interior wall761. Cavities 130-1 and 130-2 may serve as speaker volumes forrespective speakers 70. Each speaker 70 may have a respective speakerdriver 128. Speaker drivers 128 may have coils 126, magnets, and otherelectromagnetic structures that can move diaphragms 84 in response tosignals receive over acoustic signal lines 122. This produces sound thatis emitted through mesh 78 or other acoustically transparent speakerport material in speaker ports 72. Conductive gaskets 74 may run aroundthe peripheral edges of speaker ports 72 on the upper surface of support76 (e.g., gaskets 74 may be shorted to metal 52 of FIG. 5).

Signal lines 122 may be routed to carrier 76 on a signal path formedfrom flexible printed circuit 120 or other suitable signal pathstructure. If desired, circuit elements such as inductors 86 may beinterposed in the signal paths coupled to speaker drivers 128. Inductors86 may be sized to allow audible frequency signals to pass unimpeded tospeaker drivers 84 while blocking high frequency signals such as antennasignals and other radio-frequency signals, thereby reducing unwantednoise in speakers 70. There are two speakers 70 in structure 76 of FIG.6. More speaker volumes and speakers may be formed in structure 76 orfewer speaker volumes and speakers may be formed in structure 76 ifdesired. The example of FIG. 6 in which antenna 40 is formed from ahollow antenna carrier structure that includes two speaker drivers ismerely illustrative.

If desired, there may be two (or other suitable number) of antennas 40and four (or other suitable number) of speakers 70 in device 10. As anexample, one antenna 40 and an associated set of two speakers may belocated on the left half of housing 12B and another antenna 40 and itsassociated set of two speakers may be located on the right half ofhousing 12B. Structures 76 may be mounted so that each speaker port 72is aligned with a corresponding set of speaker openings 28.

Slots 30-1 and 30-2 may serve as antenna apertures for respective cavityantennas 40 (e.g., antennas that are each formed using a structure suchas structure 76 of FIG. 6). Slots 30-1 and 30-2 may be present in bothopen-lid and closed-lid configurations for device 10. An illustrativeopen-lid configuration in which slots 30-1 and 30-2 are present is shownin FIG. 1. An illustrative rear view of housing 12 showing how a slotsuch as slot 30-2 may be present in a closed-lid configuration fordevice 10 is shown in FIG. 7. As shown in FIG. 7, slots 30 such as slot30-2 may have an elongated shapes that extend parallel to axis 22.During antenna operation, wireless antenna signals that have beentransmitted by antennas 40 and wireless antenna signals that are beingreceived by antennas 40 may pass through the antenna apertures formed byslots 30-1 and 30-2.

As shown in the illustrative interior view of device 10 of FIG. 8,antennas 40 may be aligned with the apertures formed by slots 30-1 and30-2 (i.e., the right-hand antenna 40 may be aligned with slot 30-2 andthe left-hand antenna 40 may be aligned with slot 30-1). Flexibleprinted circuit(s) 31 may include one or more flexible printed circuitssuch as a camera flexible printed circuit that carries camera signals,one or two or more than two display flexible printed circuits that carrydisplay data, one or more backlight unit flexible printed circuits thatcarry power and control signals for a backlight in display 14, and/orother flexible printed circuits (e.g., a touch sensor flexible printedcircuit that carries touch sensor signals for display 14).

Antennas 40 are preferably isolated from each other (e.g., to optimizeMIMO operation). Flexible printed circuit(s) 31 may contain one or moresheets of flexible dielectric substrate material such as a layer ofpolyimide or a sheet of other flexible polymers (substrate 132). Signallines 136 may be formed in central region 138 of circuit(s) 31. The leftand right edges 140 of flexible printed circuit(s) 31 that border region138 and lines 136 may contain ground traces 134. The width of groundtraces 134 may be 1-2 mm, more than 1 mm, less than 3 mm, or othersuitable thickness. Ground traces 134 may have screw hole openings thatreceive metal screws 142. Metal screws 142 may be received withinthreaded openings in housings 12A and 12B, thereby grounding groundtraces 134 to the upper and lower portions of housing 12. The presenceof these grounded metal traces in circuit(s) 31 helps divide slot 30into separate electromagnetically isolated antenna apertures (slots 30-1and 30-2). This helps ensure that the right and left antennas 40 ofdevice 10 operate independently.

Gaskets 74 may be formed from conductive foam, conductive fabric, and/orother conductive structures (i.e., elastomeric structures that canexpand outwardly against nearby structures after being compressed). Anillustrative cross-sectional side view of conductive foam structuresthat may be used in forming gaskets 74 is shown in FIG. 9. As shown inFIG. 9, gasket 74 may be formed from one or more foam layers such aslayers 148 that are coupled together in a stack. An opening such asopening 156 (e.g., a rectangular opening formed within a stack ofrectangular foam layers) may be used to shape the layers into astructure that serves as gasket 74. (In the diagram of FIG. 9, thematerial in opening region 156 has not yet been removed.)

Foam layers 148 may each include foam substrate layers 146. The foam oflayers 146 may be a closed cell foam that helps ensure that gasket 74can serve as an acoustically isolating gasket for surrounding speakerport 74. Closed cell foam does not have openings that pass through thebody of the foam, so closed cell foam effectively blocks sound. However,the presence of the cell walls in a closed cell foam can make itchallenging to deposit metal or other conductive material into the foamin a way that forms current paths through the foam. Accordingly, foamlayers 146 may be provided with metal vias such as vias 150 that passthrough the closed cell foam. Metal vias 150 render layers 148conductive (i.e., layers 146 with vias 150 serve as conductive foamlayers in gasket 74). Conductive adhesive layers 152 may be used tocouple one, two or more, or three or more of layers 148 together and toconductive fabric 154. The number of layers 148 to be used in gasket 74may be determined by the desired thickness of gasket 74. Layers 148 maybe 0.5 mm thick, more than 0.5 mm thick, less than 0.5 mm thick, etc.Fabric 154 may be wrapped around some or all of the exterior surfaces oflayers 148 to increase the conductivity of gasket 74. Conductive fabric154 may be formed from metal fibers, metal coated plastic fibers, fiberstreated with metal particles and/or other conductive materials, etc. Ifdesired, layers 148 may be formed from open cell plastic foam platedwith metal or other suitable conductive elastomeric structures. The useof closed cell foam with metal vias to form gasket 74 is merelyillustrative.

A cross-sectional side view of antenna 40 mounted in an illustrativelocation within housing 12 in alignment with slot 30 (e.g., slot 30-1 orslot 30-2) is shown in FIG. 10. As shown in FIG. 10, antenna resonatingelement 50 and the front face of dielectric support structures 76 mayface slot 30 in direction 164 so that antenna signals from antenna 40may pass through slot 30. Conductive structures such as structures 160and 162 may be used to ground antenna ground trace 52 of antenna 40 tometal lower housing 12B. Structure 162 may be a layer of conductiveadhesive or other conductive material. Structure 160 may be a conductivefoam layer that helps press antenna 40 upwards so that gasket 74 iscompressed between ground 52 on the upper surface of carrier 76 and theopposing lower surface of the upper portion of metal lower housing 12B.The opening in the center of gasket 74 is preferably aligned withspeaker openings 28 in housing 12B and with speaker port 72. Aligningspeaker 70 with the housing speaker ports formed from openings 28 allowssound from speaker port 72 to exit device 10 (e.g., when lid 12A isopen). Gasket 74 forms an acoustic seal around speaker port 72 andprevents sound from leaking into the gap between antenna 40 and housing12B. Gasket 74 also forms a conductive path that shorts antenna ground52 of antenna 40 to the underside of the upper portion of housing 12B,thereby preventing antenna signals from entering into the interior ofhousing 12B via path 166. This helps ensure that antenna signals beingtransmitted by antenna 40 will not interfere with circuitry in theinterior of device 10 such as display circuitry for display 14, controlcircuitry 30, etc.

Upper housing 12A may have a rear portion such as portion 12AR that isseparated from lower housing 12B by a sufficient amount when device 10is in a lid-closed configuration to form gap 30 and thereby allowantenna 40 to transmit and receive wireless signals. FIG. 11 showsdevice 10 in an illustrative lid-open configuration in which upperhousing (lid) 12A has been rotated into an open position about hingeaxis 22. In the illustrative configuration of FIG. 11, slot 30 has upperand lower portions (in addition to the left and right portions locatedat different positions along axis 22). Antenna signals can pass througheither the upper portion of slot 30, through the lower portion of slot30, or through both upper and lower slots 30 of FIG. 11. With this typeof arrangement, each antenna is associated with a pair of antennaapertures (i.e., the upper slot and lower slot). If desired, eachantenna may operate through a single slot in both the open and closedlid position. The illustrative configuration of FIG. 11 in which theopen lid position for device 10 creates a pair of slot apertures foreach antenna is merely illustrative.

The varying position of housing 12A with respect to antenna 40 canimpose a variable impedance loading onto antenna 40. As a result,antenna performance can be detuned as the position of housing 12A isadjusted by a user (e.g., to optimize viewing of display 14 in housing12A). This effect is illustrated by the graph of FIG. 12 in whichantenna performance (standing wave ratio SWR) has been plotted as afunction of operating frequency fin an illustrative communications bandof interest at 2.4 GHz. The curves of FIG. 12 illustrate the impact ofincorporating capacitor 102 into the signal path between transceiver 90and antenna 40 and illustrate the impact of lid position. Curve 170illustrates the performance of antenna 40 in a configuration in whichlid 12A is open at an angle of 110° with respect to horizontal and inwhich capacitor 102 has been omitted. Curve 170′ shows how antennaperformance for this type of antenna arrangement can be detuned when lid12A is closed (i.e., oriented at 0°). Curve 168 corresponds to operationof antenna 40 in a configuration in which capacitor 102 is present andlid 12A is in an open position at 110°. In the presence of capacitor102, the bandwidth of antenna 40 is broadened as illustrated by thebroadened shape of antenna resonance curve 168 relative to the shape ofcurve 170. The broadening impact of capacitor 102 ensures that antenna40 will continue to operate satisfactorily at a desired frequency in the2.4 GHz band even when lid 12A is closed (curve 170′).

In the illustrative graph of FIG. 13, antenna efficiency has beenplotted as a function of lid position (i.e., the position of housing 12Arelative to housing 12B). Curve 174 corresponds to an antennaarrangement in which capacitor 102 has been omitted. Curve 172, whichexhibits reduced lid position sensitivity, corresponds to an antennaarrangement in which capacitor 102 has been included.

As the examples of FIGS. 12 and 13 illustrate, the use of capacitor 102helps to reduce the susceptibility of antenna 40 to lid positiondetuning effects. If desired, otherlid-detuning-susceptibility-reduction circuits may be coupled betweentransceiver 90 and the feed for antenna 40. The use of capacitor 102 tobroaden the response of antenna 40 and thereby reduce the impact ofantenna detuning is merely illustrative.

Another way in which to reduce the sensitivity of device 10 tolid-position-induced antenna detuning involves monitoring theperformance of antenna 40 and/or the position of lid 12A usingmonitoring circuitry (e.g., impedance monitoring circuitry,received-signal-strength monitoring circuitry, etc.). Antenna 40 can beprovided with tunable circuitry that can retune the antenna and therebyensure that antenna performance does not vary more than desired.

Consider, as an example, the arrangement of FIG. 14. As shown in FIG.14, device 10 may have an antenna with tuning circuitry. Tuningcircuitry 176 of antenna 40 may include adjustable inductors, adjustablecapacitors, and/or other adjustable circuitry. Tuning circuitry 176 maybe incorporated into antenna resonating element 50, a portion of antennaground 52, a parasitic element, an antenna feed structure, an impedancematching circuitry, or other wireless circuitry. Control circuitry 30may provide data to transceiver circuitry 90 when it is desired totransmit this data using antenna 40 and may process wireless data thathas been received by transceiver circuitry 90 using antenna 40. Controlcircuitry 30 may also receive data from an antenna performancemonitoring circuit and/or lid position sensor 178 (e.g., an optically,magnetically, or electrically encoded angle sensor coupled betweenhousings 12A and 12B). Based on information on the position of lid 12Aor other information on the state of antenna 40, control circuitry 30can adjust tuning circuit 176 to ensure that antenna 40 is performing asdesired.

FIG. 15 is a diagram showing how tunable circuitry such as tuningcircuit 176 can be implanted using a variable capacitor coupled betweenantenna resonating element 50 and antenna ground 52. Other types oftuning circuit (e.g., tunable inductors, etc.) can also be used. Thetuning configuration of FIG. 15 is merely illustrative.

FIG. 16 is a graph illustrating how tunable circuitry 176 may beadjusted based on information such as measured lid position. Initially,antenna 40 may be operated at desired frequency f1 with lid 12A in afirst position. Upon moving lid 12A to a second position, antenna 40 hasthe potential to become detuned, as indicated by detuned antennaresonance 182 at undesired frequency f2. By using an a lid positionsensor such as angle sensor 178 or other sensor that is sensitive to theposition of lid 12A relative to housing 12B, control circuitry 30 candetermine that antenna 40 has the potential to be detuned and thereforecan adjust tuning circuit 176 by an appropriate amount to compensate.This retunes antenna 40 so that antenna 40 exhibits an antenna resonancesuch as resonance 184 at desired frequency f1 (even though lid 12A hasbeen moved).

In general, antenna 40 may be retuned by control circuitry 30 based ondata from transceiver 90 (e.g., received signal strength or othersuitable metric), based on information form a proximity sensor, touchsensor, accelerometer, compass, or other sensor in device 10, based oninformation from a lid angle sensor, etc. The illustrative configurationof FIG. 14 in which angle sensor 178 is used to provide controlcircuitry 30 with information for adjusting tunable circuitry 176 ismerely illustrative.

The foregoing is merely illustrative and various modifications can bemade by those skilled in the art without departing from the scope andspirit of the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. A portable computer, comprising: a metal housinghaving an upper housing portion that contains a display and having alower housing portion, wherein the upper and lower housing portions areseparated by a slot-shaped opening and the lower housing portion hasopposing first and second conductive surfaces; first and second hingesthat connect the upper housing portion to the lower housing portion; andat least one cavity antenna in the lower housing portion that is alignedwith at least a portion of the slot-shaped opening, wherein the cavityantenna includes antenna traces on a dielectric support structure, theantenna traces are shorted to the first conductive surface of the lowerhousing portion through a first conductive structure that contacts thefirst conductive surface, and the antenna traces are shorted to thesecond conductive surface of the lower housing portion through a secondconductive structure that contacts the second conductive surface.
 2. Theportable computer defined in claim 1 wherein the antenna traces includean antenna resonating element and antenna ground traces.
 3. The portablecomputer defined in claim 2 wherein the dielectric support structurecomprises a hollow dielectric support structure.
 4. The portablecomputer defined in claim 3 further comprising at least one speakerdriver in an interior volume within the hollow dielectric supportstructure, wherein the hollow dielectric support structure has a speakerport that is aligned with the speaker driver.
 5. The portable computerdefined in claim 4 wherein the lower housing portion has at least onespeaker opening that is aligned with the speaker port in the hollowdielectric support structure.
 6. The portable computer defined in claim5 further comprising a ring-shaped gasket that surrounds the speakerport and that is compressed between the hollow dielectric supportstructure and the lower housing portion.
 7. The portable computerdefined in claim 2 wherein the antenna resonating element has first andsecond branches that resonate in first and second communications bandsand the antenna traces further comprise a parasitic antenna resonatingelement on the dielectric support structure that resonates in the secondcommunications band.
 8. The portable computer defined in claim 1 furthercomprising: a tunable circuit coupled to the cavity antenna; a lid anglesensor that measures how much the upper housing portion is angled withrespect to the lower housing portion; and control circuitry that adjuststhe tunable circuit to adjust the cavity antenna at least partly inresponse to measurements from the lid angle sensor.
 9. The portablecomputer defined in claim 1 further comprising a flexible printedcircuit having first and second ground traces that are shorted to theupper housing portion with screws and that are shorted to the lowerhousing portion with screws, wherein the first ground trace and thefirst hinge form first and second ends of an antenna aperture for thecavity antenna and wherein signal lines are formed on the flexibleprinted circuit between the first and second ground traces.
 10. Theportable computer defined in claim 1, wherein the first conductivestructure comprises a conductive gasket that is compressed between thefirst conductive surface of the lower housing portion and the antennatraces on the dielectric support structure.
 11. The portable computerdefined in claim 10, wherein the second conductive structure comprisesconductive foam that shorts the antenna traces on the dielectric supportstructure to the second conductive surface of the lower housing portion.12. The portable computer defined in claim 1, wherein the antenna tracescomprise an antenna resonating element and ground traces, a firstportion of the ground traces is shorted to the first conductive surfaceof the lower housing portion using the first conductive structure, asecond portion of the ground traces is shorted to the second conductivesurface of the lower housing portion using the second conductivestructure, the first conductive surface of the lower housing portioncomprises speaker openings, the first portion of the ground tracescomprise a speaker port aligned with the speaker openings, the speakerport is formed on a first side of the dielectric support structure, thesecond portion of the ground traces is formed on a second side of thedielectric support structure that is different from the first side, andthe antenna resonating element is formed on a third side of thedielectric support structure that is different from the first and secondsides.
 13. A portable computer, comprising: a metal housing having anupper housing portion that contains a display and having a lower housingportion, wherein the upper and lower housing portions are separated by aslot-shaped opening; first and second hinges at opposing ends of theslot-shaped opening that connect the upper housing portion to the lowerhousing portion; a flexible printed circuit with ground traces that areshorted to the upper and lower housing portions to divide theslot-shaped opening into first and second slots; and first and secondcavity antennas in the lower housing portion that are alignedrespectively with the first and second slots, wherein the first andsecond slots serve as respective antenna apertures for the first andsecond cavity antennas.
 14. The portable computer defined in claim 13wherein the first and second cavity antennas each comprise: antennatraces on a hollow dielectric support structure containing a pair ofspeakers, each speaker having a speaker port aligned with acorresponding set of speaker openings in the lower housing portion. 15.The portable computer defined in claim 14 further comprising ring-shapedconductive gaskets each of which surrounds a respective one of thespeaker ports and acoustically seals the speaker port to the lowerhousing portion.
 16. The portable computer defined in claim 15 whereinthe antenna traces include ground antenna traces and wherein theconductive gaskets comprise closed cell foam and electrically short theground antenna traces to the lower housing portion.
 17. The portablecomputer defined in claim 16 wherein the upper housing portion ispositioned at an angle relative to the lower housing portion with thefirst and second hinges and wherein at least some of the slot-shapedopening is formed between the upper housing portion and the lowerhousing portion both when the upper housing portion is parallel to thelower housing portion and when the upper housing portion is not parallelto the lower housing portion.
 18. A portable computer, comprising: ametal base housing containing a keyboard; a metal lid containing adisplay having a planar surface; hinges that couple the metal lid to themetal base housing, wherein a slot-shaped opening is formed between themetal base housing and the metal lid; and an antenna that conveysradio-frequency signals through the slot-shaped opening, wherein themetal lid comprises a first portion, a second portion, and a thirdportion, the display is located in the first portion, the second portionextends from the first portion to the third portion at a non-parallelangle with respect to the planar surface of the display, the thirdportion extends at a non-parallel angle with respect to the secondportion, and the third portion defines an edge of the slot-shapedopening.
 19. The portable computer defined in claim 18 wherein theantenna includes a hollow plastic support structure covered with antennatraces.
 20. The portable computer defined in claim 19 wherein the hollowplastic support structure has a pair of speakers aligned with respectivespeaker ports in the hollow plastic support structure.
 21. The portablecomputer defined in claim 20 wherein the metal base housing has aplurality of speaker holes that overlap the speaker ports.
 22. Theportable computer defined in claim 21 wherein each speaker port issurrounded by a conductive gasket that shorts at least some of theantenna traces to the metal base housing and that acoustically sealsthat speaker port against the metal base housing.
 23. The portablecomputer defined in claim 18, wherein the hinge configures the metal lidto rotate with respect to the metal base housing about a rotational axisand the rotational axis extends through the second portion of the metallid.
 24. The portable computer defined in claim 23, wherein the metallid is configured to rotate between an open position and a closedposition, the planar surface of the display lies parallel to thekeyboard when the metal lid is in the closed position, the secondportion of the metal lid has a first end connected to the first portionof the metal lid and a second end connected to the third portion of themetal lid, and the third portion of the metal lid extends from thesecond end of the second portion of the metal lid at a non-parallelangle with respect to the planar surface of the display.